This invention relates to a method and apparatus for manufacturing a color filter by coloring a color filter substrate, the color filter, a display device using the color filter, and an apparatus equipped with the display device.
Recent advances in personal computers, especially portable personal computers, have been accompanied by increasing demand for liquid crystal displays, particularly color liquid crystal displays. However, lowering the cost of liquid crystal displays is required to further the wider use thereof, and it is particularly important to lower the cost of color filters, which are relatively expensive. Various methods of meeting these demands while satisfying the characteristics required of color filters have been tried, but a method of satisfying all of these requirements has not yet been realized. The various methods that have been attempted will now be described.
A first method, which is that most widely used, is dyeing. This method includes coating a glass substrate with an aqueous polymer material consisting of a dyeing material, patterning the polymer material into a desired shape by photolithography and then dipping the pattern obtained into a dye solution to obtain a colored pattern. By repeating this three times, R (red), G (green), B (blue) color filter layers are formed.
A second method is pigment dispersion, which currently is in the process of supplanting the dyeing method. This method includes forming a photosensitive resin layer, in which a pigment has been dispersed, on a substrate, and patterning this layer to obtain a pattern of a single color. By repeating this three times, R, G, B color filter layers are formed.
A third method is electrodeposition. This method includes forming transparent patterns on a substrate and electrodepositing a first color by dipping the substrate in an electrodeposition coating solution containing pigment, resin and an electrolyte, etc. Color filter layers of the colors R, G, B are formed by repeating this process three times. This is followed by calcination.
A fourth method is printing. This includes dispersing pigment in a thermosetting resin and repeating printing three times to apply the three colors R, G, B, after which the resin is thermoset to form colored layers.
In general, a protective layer is formed on the colored layers in each of the methods mentioned above.
What these methods have in common is that it is required that the same process be repeated three times in order to achieve coloring in the three colors R, G, B. This increases cost. An additional problem is that the greater the number of steps, the lower the yield. Furthermore, in the electrodeposition method, the shapes of the patterns that can be formed are limited. For this reason, this method cannot be applied to TFT applications. The printing method cannot form patterns at a fine pitch owing to poor resolution and smoothness.
To eliminate these shortcomings, methods of manufacturing color filters using an inkjet method have been disclosed in the specifications of Japanese Patent Application Laid-Open (KOKAI) Nos. 59-75205, 63-235901 and 1-217320. These methods include spraying coloring solutions, which include pigments of the three colors R, G, B, on a light-transmitting substrate by the inkjet method and drying each of the coloring solutions to form a colored image area. The inkjet method makes it possible to form R, G, B pixels at one time. The advantages obtained are a greatly simplified manufacturing process and a major reduction in cost.
However, in the conventional method of manufacture based upon the inkjet method described above, a series of steps from a step for forming an ink-absorbing receptor layer on a color filter substrate to a step for coloring the receptor layer and curing the receptor layer is not performed continuously. The result is poor productivity.